Method of removing metal from the surface of blooms and the like



Patented May 11, 1948 METHOD OF REMOVING METAL FROMTHE SURFACE OFBLOOMS-AND THE-LIKE- James L. afitiaseit ciosteen, 11., assigns-tami-Reduction Company, Incorporated, acamera tion bf New York No Drawing.Application. July 21 1945, Serial N0. 606,477

. l This;inventionrelates to the thermo-che'inical removal of metal fromthe surface of blo'oms,

billets, slabsand other metal bodies. This operation is sometimesreferred to as scarfing.

when blooms, billets and other rolled metal bodiesccjme from the rollingmills they usually have surface imperfections and adhering oxideandscale Scarflng is performed on the metal bodies toremove a layer ofthe surface metalan'd thereby remove the surface imperfections beforethe finalrolling operations. A common way of 'perferrning thescarfingoperation is to project against the surface to be scarfed, while themetal is at kindling temperature, oxygen streams deby a burner block,and causing relative movement of the surface and the oxygen streams sothat the oxygen progressively removes the surface metal. Before thescarfing operation can be started the portion of the surface where thescarflhg is to beinitiated must be conditioned by' removing the oxideand scale. This is usually accomplished by the use of heating flameswhich issue from the burner and which are projected 'ga'inst the surfaceto fuse the oxide and scale and thereby initiate the scarfing operationwhen the scarfing oxygen is turned on. Heretofore some. delay has beenexperienced in starting the scar'fing operation because of the timerequired t6 fuse the oxide and scale. Because of the ins'iflating effect"of the oxide and scale, and because of the tendency of the oxide tobuild up when using heating flames of the usual character, it has beennecessary to heat the oxide and seale fer a tense ranging anywhere from13' to seconds before the scarfing operating could be started.

The principal object of this invention is to so modify the usual methodof removing metal from the surface of metal bodies having adhering oxideand scale that the time required for the heating andsurface-conditioning step is greatly reduced or entirely eliminated.

According to the invention the heating of the surface where the scarfingis to be initiated is performed by the use of oxyacetylene flame jetswhich have a reducing action. The supply of" oxygen and acetylene to theflame jets is adjusted so that there is an excess of acetylene toproduce reducing flames having a so-called acetylene feather which ispreferably sufficiently long to extend to the surface to be scarfed.

The film or layer of oxide on the surface of a hot bloom or billet isusually at a temperature of 2000 F. or higher and the reducing flamesact instantly on it and change the oxide to metallic 5' dlailiis. (Cl:148.29

iron. The film 'of oxide may be changed into particles "of iron whichco'ale'sce'intomolten globu'les, orit'm'ay be changed into a film ofmetallic iron which is caused to form intomolten globules by surfacetension. In either case when the oxygen is turned 'on, the globules ofmetallic iroiiburn and create a temperature considerably above the"temperature of 'tl'ie'h'ot' bloom and cause the surfacemetal 6f thebloomto ignite iininediately. They act like anum-ber of starting rodsproducing instantaneous action. Asthe globules ignite they are forciblypre sed against the surfab'e 6f the bloom by the sc'aifing oxygenstreams 'so' that the" ignition of the-surface metal 'cf-the bloom andthe globules is "simultaneous. The bloom being at a temperature ofapproximately 2000 F. iswell above the critical ignition point 6f thesteel, and when the oxide is reduced to globules of metallic iron'having'the action above described, the. surface ni etalti'f'the niacinis ready for iiis taiit ignition without 'piheating. It willthu's-beseen that almost instantly after the 'i'ediicing fiamesare projectedagainstthe i'agyercf exide anascaie the sear'fiii oxygen can be turnedon andthe scarrin o eration star-ted, Wheiby'th reduetibi'i -(jfthloxi'de takes iacejat a temperature bf'elbw its "fusion pointand-theberio'd of time heretofore required for the 'flames a ruse theime" and scale is liiiiifiat d. Prfimy, the 'leiilluiiig fifiiactr ofthe 'flalhes'is' maintaineduurin the entire scafrfin'g operation. A V woxyacet lene flames 'a'djustedso that they'are refitting incharacter-practice"alessiiitense heat,

of course, than neutral flames. For this reason, and because of thepresence of the oxide and scale on the surface to be scarfed, one wouldnaturally be led away from the use of reducing flames for the usualpreliminary heating operation. It would be expected that they are eithernot hot enough to be useful at all for such operation, or would undulylengthen the time required for its performance. Contrary to theseexpectations I have discovered that despite their less heat intensityreducing flames actually lessen the time required for conditioning thesurface to be scarfed to such an extent that when scarring hot blooms orbillets the scarfing can be started instantly after the flames arebrought into contact with the work surface.

While the method is particularly suited for the scarfing of hot blooms,billets, slabs and the like, and has been described in that connection,it may also be used for scarfing cold work-pieces having adhering oxideand scale. In this case,

however, it may be necessary to wait a few sea onds after bringing theflames into contact with the layer of oxide and scale before thescarfing oxygen is turned on, but not nearly so long as would benecessary if the flames were of the usual neutral character.

I claim:

1. The method of desurfacing blooms, billets, slabs, and other metalbodies having adherent oxide and scale, which comprises reducing theoxide on the surface of themetal body at the place where the desurfacingoperation is to begin to molten metallic iron by projecting reducing.fiames against the surface at that place, and,

after the oxide at that place on the surface has been reduced to moltenmetallic iron, and while iit still is in such molten state, projectingan oxyjface at that place, and, after the oxide at that place on thesurface has been reduced to molten metallic iron and while it still isin such molten :state, projecting an oxygenstream againstthat place on'the surface, and then causing relative movement of the surface andoxygen stream at such relative rate as to remove the surface only of theobject.

3. The improvement in the starting of the desurfacing of blooms,billets, slabs and other metal bodies having adherent oxide and scale byprojecting an oxygen stream against a heated surface thereof andrelatively moving the surface and oxygen stream to progressively removethe surface only of the body which comprises heating the surface at thatplace where the desurfacing operation is to begin to a temperature atwhich the adherent oxide will reduce to molten metal when in contactwith a reducing gas, but below.

the fusion point of the oxide, and projecting onto .the thus heatedsurface a reducing gas'to substantially instantly reduce the oxide tomolten ymetallic iron, and immediately thereafter projecting the oxygenstream against .the surface at }.that place and proceeding with thedesurfacing 7 and oxygen stream to progressively remove the surface onlyof the body which comprises heating the surface at that place where thedesur facing operation is to begin to a temperature at which theadherent oxide will reduce to molten metal when in contact with areducing gas, but

below the fusion point of the oxide, and projecting onto the thus heatedsurface a flame fed by a mixture of oxygen and acetylene in which thereis an excess of acetylene to substantially instantly reduce the oxide tomolten metallic iron, and immediately thereafter projecting the oxygenstream against the surface at that place and proceeding with thedesurfacing operation, whereby the reduction of the oxide takes place ata temperature below its fusion point and without preliminary fusingthereof.

5. In the method of desurfacing hot blooms, billets, slabs, and othermetal bodies having adherent oxide and scale by projecting an oxygenstream against the surface while the metal-is at a kindling temperatureand relatively moving the surface and oxygen stream to progressivelyremove the surface metal, the improvement in starting the operationwhich comprises first reducing the oxide on the portion of the surfaceon which the oxygen stream initially is to be projected to moltenmetallic iron by projecting against such portion of the surface flameswhich are reducing in character, and then projecting the oxygen streamagainst the portion of such surface containing the molten metallic iron.

JAMES L. ANDERSON.

7 REFERENCES CITED The following references are of record in the OTHERREFERENCES Metals Handbook, 1936 edition, page 138,,(pub. by AmericanSociety for Metals, Cleveland, Ohio).

